| Owing to the risk of bronchoconstriction, non-selective beta-blockers such as Trasicor/Slow Trasicor should be used with particular caution in patients with chronic obstructive lung disease. (see Contra-indications). As beta-blockers increase the AV conduction time, beta-blockers should only be given with caution to patients with first degree AV block. Beta-blockers should not be used in patients with untreated congestive heart failure. This condition should first be stabilised. If the patient develops increasing bradycardia less than 50-55 beats per minute at rest and the patient experiences symptoms related to bradycardia, the dosage should be reduced or gradually withdrawn (see Contra-indications). Beta-blockers are liable to affect carbohydrate metabolism. Diabetic patients, especially those dependent on insulin, should be warned that beta-blockers can mask symptoms of hypoglycaemia (e.g. tachycardia) (see Interactions with other medicaments and other forms of interaction). Hypoglycaemia, producing loss of consciousness in some cases, may occur in non-diabetic individuals who are taking beta-blockers, particularly those who undergo prolonged fasting or severe exercise. The concurrent use of beta-blockers and anti-diabetic medication should always be monitored to confirm that diabetic control is well maintained. Beta-blockers may mask certain clinical signs (e.g. tachycardia) of hyperthyroidism and the patient should be carefully monitored. Beta-blockers may reduce liver function and thus affect the metabolism of other drugs. Like many beta-blockers oxprenolol undergoes substantial first-pass hepatic metabolism. In the presence of liver cirrhosis the bioavailability of oxprenolol may be increased leading to higher plasma concentrations (see Pharmacokinetic properties). Patients with severe renal failure might be more susceptible to the effects of anthihypertensive drugs due to haemodynamic effects. Careful monitoring is advisable (see Pharmacokinetic properties). In patients with peripheral circulatory disorders (e.g. Reynaud's disease or syndrome, intermittent claudication), beta-blockers should be used with great caution as aggravation of these disorders may occur (see Contra-indications). In patients with phaeochromocytoma a beta-blocker should only be given together with an alpha-blocker, (see Contra-indications). Owing to the danger of cardiac arrest, a calcium antagonist of the verapamil type must not be administered intravenously to the patient already receiving treatment with a beta-blocker. Furthermore, since beta-blockers may potentiate the negative-inotropic and dromotropic effects of calcium antagonists, like verapamil or diltiazem, any oral co-medication (e.g. in angina pectoris) requires close clinical control (see also Interactions with other medicaments and other forms of interaction). Anaphylactic reactions precipitated by other agents may be particularly severe in patients taking beta-blockers, especially non-selective drugs, and may require higher than normal doses of adrenaline for treatment. Whenever possible, beta-blockers should be discontinued in patients who are at increased risk for anaphylaxis. Especially in patients with ischaemic heart disease, treatment should not be discontinued suddenly. The dosage should gradually be reduced, i.e. over 1-3 weeks, if necessary, at the same time initiating alternative therapy, to prevent exacerbation of angina pectoris. If a patient receiving oxprenolol requires anaesthesia, the anaesthetist should be informed of the use of the medication prior to the use of general anaesthetic to permit him to take the necessary precautions. The anaesthetic selected should be one exhibiting as little inotropic activity as possible, e.g. halothane/nitrous oxide. If on the other hand, inhibition of sympathetic tone during the operation is regarded as undesirable, the beta-blocker should be withdrawn gradually at least 48 hours prior to surgery. The full development of the oculomucocutaneous syndrome, as previously described with practolol has not been reported with oxprenolol. However some features of this syndrome have been noted such as dry eyes alone or occasionally associated with skin rash. In most cases the symptoms cleared after withdrawal of the treatment. Discontinuation of oxprenolol should be considered, and a switch to another antihypertensive drug might be advisable, see advice on discontinuation above. | |